PROJECT SUMMARY A transient ischemic attack (TIA) is a brief episode of neurologic dysfunction. The conventional viewpoint is that there are no residual motor deficits following a TIA. However, recent evidence suggests that individuals who have a TIA have impairments in activities of daily living and driving. These activities require robust motor control. Our preliminary data suggest that compared with healthy adults, individuals with TIA exhibit greater movement variability during isolated ankle dorsiflexion, greater stride length variability during over ground walking, greater lane maintenance variability during a simulated road driving task, and greater brake force variability during a reactive driving task. In addition, individuals with a TIA exhibit greater variability of the neural activation and greater co-activation of the agonist and antagonist muscles. Based on these findings, we test the central hypothesis that TIA impairs motor control, over ground walking, driving, and the neural activation of muscle. To address this hypothesis we propose the following two specific aims. In Aim 1, we will determine whether individuals who had a TIA exhibit deficits in motor control compared with healthy age-matched controls. To accomplish this aim, we will recruit 30 individuals 1-5 weeks post TIA and 30 age matched controls. We will quantify deficits in motor control during isolated ankle dorsiflexion, over ground walking, simulated road driving, and reactive driving. We hypothesize that individuals with a TIA will exhibit greater motor output variability during the isolated ankle dorsiflexion tasks, greater walking variability, and deficits in road driving and reactive driving performance. In Aim 2, we will determine whether individuals who had a TIA exhibit altered neural activation of muscle compared with healthy age-matched controls. To accomplish this aim, we will test the same individuals as in Aim 1. We will examine single- and multi-motor unit discharge rate and agonist and antagonist muscle activity. We hypothesize that individuals with TIA will exhibit greater single- and multi-motor unit discharge rate variability, greater agonist and antagonist muscle variability, and greater coactivation for the agonist and antagonist muscles than healthy controls. This proposal will be the first to identify whether individuals who had a TIA exhibit residual functional motor control deficits. It is essential because the incidence of TIA is expected to increase dramatically leading to increased number of falls and driving accidents, and contribute significantly to health-related expenses.